The present disclosure relates generally to circuit breakers and particularly to circuit breaker operation mechanism attachment arrangements.
Multipole circuit breakers configured to protect multiphase electrical circuits are known in the electrical circuit protection industry. The variety of constructions of multipole circuit breakers include blow open and non-blow open contact arms, overcentering and non-overcentering contact arms, single contact pair arrangements with the contact pair at one end of a contact arm and a pivot at the other end thereof, double contact pair arrangements (referred to as rotary breakers) with a contact pair at each end of a contact arm and a contact arm pivot intermediate (typically centrally located between) the two ends, single housing constructions with the circuit breaker components housed within a single case and cover, and cassette type constructions (referred to as cassette breakers) with the current carrying components of each phase housed within a phase cassette and each phase cassette housed within a case and cover that also houses the operating mechanism. Multipole circuit breakers are generally available in two, three, and four pole arrangements, with the two and three pole arrangements being used in two and three phase circuits, respectively. Four pole arrangements are typically employed on three phase circuits having switching neutrals, where the fourth pole operates to open and close the neutral circuit in a coordinated arrangement with the opening and closing of the primary circuit phases.
An amount of energy available to close the contact arms is typically related to forces exerted by springs included within an operating mechanism of the circuit breaker. One manner to increase this energy is to increase a size of the springs, which typically results in an accompanying undesired increase of mechanism size. Further, many circuit breakers commonly employ operating mechanisms that incorporate components disposed proximate the contact arms, such as central pivots and cross pins that extend in a direction along an axis of a rotor and are disposed across multiple poles of the circuit breaker, proximate more than one set of contact arms corresponding to more than one pole. As a length of the cross pins, utilized to drive rotors that correspond to each of the phases, from the operating mechanism increases, deflection of the cross pins can allow contact depression variation between different phases, thereby resulting in contact resistance variation. Further, openings between separate poles to allow for disposal of central pivots and cross pins may reduce a dielectric strength between poles of the circuit breaker. While existing circuit breakers are considered suitable for their intended purpose, the art of circuit breakers may be improved by providing an operating arrangement that overcomes these drawbacks.